This invention relates generally to control systems and methods for work machines and, more particularly, to a system and method for controlling the operation of a plurality of fans positioned in an arrangement to provide cooling for a plurality of heat transfer cores positioned therearound.
Construction and earthmoving equipment as well as a wide variety of other types of work machines are commonly used in a wide variety of construction and earthmoving applications. Heat is a natural by-product of the engine and the other functional equipment associated with work machines and must therefore be dissipated efficiently in order to keep the engine and other equipment within proper operating temperature limits for optimum and continued sustained performance. As a result, a wide variety of different types of cooling systems are utilized to accomplish this task. Controlled heat dissipation through a properly controlled cooling system optimizes the performance of the overall work machine as well as the performance of the functional mechanical components associated therewith.
Using one or more fans for cooling a plurality of heat transfer cores in a work machine is quite common. When a single fan is utilized, such a fan is typically installed in series with a plurality of heat exchanger cores. Such prior art fan configurations typically impede optimal heat dissipation and optimal positioning of the heat exchanger cores and adversely affect the efficiency and balance of the overall machine. Such prior art designs also add to the overall size of the machine which must be kept to a minimum due to space limitations as well as dimensional constraints on operator visibility. In this regard, the packaging length of the cooling system is typically limited by the axial spacing of the power train components and the width of such system is typically limited by the existing frame rail dimensions. Such serial positioning of the heat exchanger cores also makes it difficult to clean out debris carried by the air flow and blown into the fins of the various serially positioned heat exchanger cores. Debris collected in the fins insulates the transfer of heat therefrom thereby adversely impacting the performance and efficiency of the heat dissipation equipment and the overall machine.
Utilizing a single fan to provide cooling to a plurality of heat exchanger cores also requires use of a larger diameter fan to accomplish the necessary cooling. This typically translates into a larger axial length since fan depth typically increases with fan size. This arrangement likewise adds to the overall size of the cooling system and the machine.
When a plurality of fans are utilized to cool a plurality of heat transfer cores, these fans are usually driven directly off of the engine of the work machine with a drive belt or other mechanism whereby fan speed is a direct function of the speed of the work machine engine. In such prior art fan control systems, cooling of the heat transfer cores may occur even when cooling is not desired. No speed reduction capability when cooling is not required consumes unnecessary power which could be used for useful work. In addition, most fans tend to run unnecessarily in cold weather tending to overcool fluids like hydraulic oil, transmission oil, and engine coolant. Similarly, undesired cooling at any time can also cause the fluids carried by the heat transfer cores to reach an undesirable overcooled condition. When this occurs, work machine performance is not only degraded, but operation of the cooling system under such circumstances is unnecessary, inefficient and results in unnecessary fuel consumption and wasted power. Besides causing unnecessary fuel consumption, undesired fan operation adds to the noise emissions of the overall work machine. Furthermore, the functional components served by the fluid in an overcooled heat transfer core are also overcooled, causing both reliability and performance problems for such components and therefore for the overall work machine.
Although known control systems for cooling heat transfer cores do employ means for controlling the operation of the cooling fans based upon certain temperature conditions associated with the heat transfer conditions associated with the heat transfer cores, such known means do not always provide cooling airflow only to the degree required, and such known means are not always sufficiently responsive to changes in the fluid temperature of the heat transfer cores without overshooting temperature design limits. Such known systems likewise do not always prevent overcooling of fluids in the respective heat transfer cores served by them.
It is therefore desirable to provide a cooling fan control system which will control the operation of a plurality of fans for cooling a plurality of heat transfer cores in a work machine so as to provide air flow only to the degree required, which is responsive enough to rapid changes in the temperature of the fluid in the heat transfer cores served by each fan without overshooting temperature design limits, which prevents overcooling of fluids in the respective cores served by each respective fan, and which minimizes fuel consumption and noise emissions of the overall work machine.
Accordingly, the present invention is directed to overcoming one or more of the problems set forth above.
In one aspect of this invention, a control system for controlling the speed of a plurality of fans for cooling a plurality of fluids in a work machine, each of the plurality of fluids being operative between a predetermined minimum threshold temperature and a predetermined maximum threshold temperature is disclosed. The control system includes a plurality of sensors positioned to sense the temperature of each of the plurality of fluids, each sensor being operable to output a signal indicative of the temperature of that particular fluid, an electronic controller coupled with the plurality of sensors for receiving signals therefrom, the controller being operable to receive a signal from each of the plurality of sensors indicative of a temperature for each of the plurality of fluids, the controller being further operable to determine a desired fan speed for each of the plurality of fans based upon signals received from the plurality of sensors, and the controller outputting a signal to each of the plurality of fans to individually control the speed thereof, each output signal being indicative of a desired fan speed for a particular fan and each output signal being based upon a comparison of at least some of the signals received from the plurality of sensors.
In another aspect of this invention, a method for controlling the speed of a plurality of fans for cooling a plurality of fluids in a work machine, each of the plurality of fluids being operative between a predetermined minimum threshold temperature and a predetermined maximum threshold temperature is disclosed. The method includes the steps of positioning a plurality of sensors to sense the temperature of each of the plurality of fluids, each sensor being operable to output a signal indicative of the temperature of that particular fluid, coupling an electronic controller with the plurality of sensors for receiving signals therefrom, the controller being operable to receive a signal from each of the plurality of sensors indicative of a temperature for each of the plurality of fluids, operably determining a desired fan speed for each of the plurality of fans based upon signals received from the plurality of sensors utilizing the controller, and outputting a signal to each of the plurality of fans to individually control the speed thereof utilizing the controller, each output signal being indicative of a desired fan speed for a particular fan and each output signal being based upon a comparison of at least some of the signals received from the plurality of sensors.